The present invention relates generally to reference voltage circuits and in particular the present invention relates to temperature controlled gain adjust circuits.
Integrated circuits form the basis for many electronic systems. Essentially, an integrated circuit includes a vast number of transistors and other circuit elements that are formed on a single semiconductor wafer or chip and are interconnected to implement a desired function. The complexity of these integrated circuits requires the use of an ever increasing number of linked transistors and other circuit elements.
Integrated circuits such as memory devices, microprocessors, controllers and application-specific integrated circuits (ASIC""s) often include internal voltage regulator circuits. These internal voltage regulators provide an internal reference voltage, often referred to as VCCR. Because the integrated circuits are operating at relatively low voltages, the internal voltage regulator performance can be adversely affected by variations in temperature. It is desired to provide a reference voltage which increases in value as temperature increases.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an integrated circuit voltage regulator which compensates for temperature variations.
The above mentioned problems with integrated circuit voltage regulators are addressed by the present invention and will be understood by reading and studying the following specification.
In one embodiment, an integrated circuit voltage regulator comprises an amplifier circuit having a first input coupled to receive an input voltage and provide an output voltage at an output node, and a gain adjust circuit connected to the amplifier circuit for adjusting a gain of the amplifier circuit. The gain adjust circuit comprises a voltage divider circuit having first and second series coupled resistors. The first resistor has a first temperature coefficient and the second resistor has a second temperature coefficient which is different from the first temperature coefficient such that a voltage on a node intermediate the first and second series coupled resistors changes in response to temperature changes experienced by the first and second series coupled resistors.
In another embodiment, a memory device comprises an array of memory cells, control circuitry for controlling read and write access operations on the memory cells, and a voltage regulator. The voltage regulator comprises an amplifier circuit having a first input coupled to receive an input voltage and provide an output voltage at an output node, and a gain adjust circuit connected to the amplifier circuit for adjusting a gain of the amplifier circuit. The gain adjust circuit comprises a voltage divider circuit having first and second series coupled resistors. The first resistor has a first temperature coefficient and the second resistor has a second temperature coefficient which is different from the first temperature coefficient such that a voltage on a node intermediate the first and second series coupled resistors changes in response to temperature changes experienced by the first and second series coupled resistors.